1. Field of the Invention
The present invention relates to a shoe attached with a grounding device, and more particularly to an anti-static sole.
2. Description of the Prior Art
Generally speaking, the phenomenon that charge transfer occurs when an insulator accumulated with charges is brought into contact with a conductor, or charge transfer occurs and potential difference is produced when two objects rub each other is called static electricity. The static electricity generally has no effect on the human body, but it will cause damage to precision equipments such as electronic elements or magnetic memory card. Therefore, the person who processes the electronic elements or the magnetic memory cards must clear the static charges from his body before work. Conductive shoe is one of the existing equipments for eliminating the static charges on the person.
Conventionally, the existing conductive shoe is provided with a ceramic resistor between a midsole and an insole of a sole, and the ceramic resistor is connected to the midsole and the insole, respectively to allow the static charges on the user to be conducted to the midsole through the ceramic resistor and then conducted to the ground from the midsole. By such arrangements, the static charges on the user can be partially eliminated such that the remaining static charges cannot cause any damage to the electronic elements or magnetic memory cards.
However, the ceramic resistor is made up of a middle ceramic portion and two metallic wires at both ends of the middle ceramic portion, and the connecting structures for connecting the ceramic portion and the two metallic wires are quite fragile, so that after being bent for many times or pressed for a long time, the metallic wires will be damaged or even broken, and the ceramic portion is likely to rupture due to overlarge pressure applied by the user. If the user finds the above defects, he must replace his shoes, but if the user fails to find the above defects, the static charges on the user cannot be eliminated properly, inevitably causing damage to the electronic elements or magnetic memory cards.
Hence, U.S. Pat. No. 6,421,222, entitled “PRECISION FAIL-SAFE ELECTROSTATIC DISSIPATING DEVICE”, disclosed an apparatus for dissipating static charges which is constructed of several conductive layers and a set of parallel resistors, if either resistor of the parallel resistor fails, the static charges can also be dissipated through the remained resistors, ensuring fail-safe dissipation of static electricity, but it can be found that the production cost is greatly increased due to the increase of the number of the resistors.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.